Market analysts said that the timing of the launch is expected to spark buying at a time when husbands or boyfriends tend to buy pink-colored gifts to please their wives or girlfriends on Valentine's Day.

In mid-January, HTC unveiled two new models -- the bigger HTC U Ultra and the smaller HTC U Play -- in Taipei as part of the company's efforts to stimulate consumers' interest and boost sales.

The U series has replaced the HTC One series as the firm's flagship model.

Sales of the 5.7-inch U Ultra began in Taiwan Jan. 25, and in Hong Kong Feb. 7. Global sales will kick off in Europe at the end of this month.

In Taiwan, 20,000 units of the U Ultra model were sold out in a pre-order sales campaign held last month, with a starting price of NT$23,900 (US$771). HTC had previously provided three colors -- ice white, sapphire blue, and brilliant black -- without the presence of pink.

According to HTC, the sapphire blue has been most welcomed by consumers in Taiwan, followed by brilliant black and ice white.

The 5.7-inch HTC U Ultra is a high-end model. The phone is equipped with a Qualcomm Snapdragon 821 processor and storage options of 64GB and 128GB.

The U Ultra model has a 12-megapixel UltraPixel rear camera with 16-megapixel front-facing camera and a 3000mAH battery. It also does away with the headphone jack.

HTC said that it will launch pre-order sales for a special version of the 128GB sapphire blue U Ultra later this month with a price tag of NT$28,900.

The mid-range 5.2-inch HTC U Play is equipped with a MediaTek (聯發科) Helio P10 processor with storage options of 32GB and 64GB. It also has a 16-megapixel rear camera and a 16-megapixel front camera.

HTC has not announced yet when the model will go on sale.

The smartphone vendor said that it hopes that the U series will boost its sales at a time when the company is facing escalating competition in the global market in both the high-end and mid-range segments.

In January, HTC posted NT$4.66 billion in consolidated sales, down 27 percent from a month earlier and also down 28 percent from a year earlier. The January figure was the lowest in 10 months.